Generally, a hydro-forming method is performed at room temperature, e.g., in a temperature range of 10 to 30 degrees Celsius, and is one of the types of forming methods which perform expansion forming of a tube member using a hydraulic pressure. Through such a hydro-forming method, a weight of press-manufactured product that is formed as a combination of unit panels such as a front side member of a vehicle can be decreased and a manufacturing cost for the same can be reduced.
Recently, tube components that are formed through hydro-forming are generally made of high strength aluminum alloy instead of steel material to decrease weight. Such an aluminum alloy has poorer forming characteristics at room temperature than the steel material, but forming characteristics of such an aluminum alloy can be improved through a softening process. The softening process means a process to decrease a strength of the aluminum alloy as well as increase an elongation ratio of the aluminum alloy, and an annealing process is generally used as the softening process.
In order to obtain sufficient forming characteristics of the tube component that is made of a metal alloy such as an aluminum alloy, a sufficient elongation ratio must be obtained in consideration of a portion that has a maximum amount of deformation according to a shape of a formed component. The softening process is inevitable to obtain such an elongation ratio.
Referring to FIGS. 8 to 12, in a conventional hydro-forming method for an aluminum alloy, a softening process for an aluminum alloy tube component 100 to obtain a sufficient elongation ratio is performed at step S110.
Subsequently, as shown in FIG. 9, at step S120, the tube component 100 is loaded on a lower mold 101. Then, as shown in FIG. 10, at step S130, an upper mold 103 has been descended so that the upper and lower molds are joined together, and hydraulic pressure cylinders 105 and 107, which are disposed on both sides of the tube component 100, are operated to compress the tube component 100 in an axial direction thereby forming a sealing within the tube component 100.
Then, as shown in FIG. 11, at step S140, a forming hydraulic fluid is supplied into the tube component 100 from the hydraulic pressure cylinders 105 and 107. Consequently, the tube component 100 is expanded to forming surfaces 109 and 111 that are formed on the upper mold 103 and the lower mold 101.
After the tube component 100 is formed, the tube component is extracted from the lower and upper molds 101 and 103 at step S150. In addition, a hardening process for the tube component 100 is performed to increase a strength of the tube member that is weakened by the softening process. Such a hardening process may deteriorate a quality of the formed tube component and a productivity of the forming process.
Meanwhile, a warm hydro-forming method has been introduced, in which a tube component is heated in order to increase the forming characteristics of the tube component. A warm hydro-forming device for performing a warm hydro-forming method generally comprises heating means such as heating coils that are disposed within an upper mold and a lower mold.
However, conventional heating means were not effective for heating the tube member. In particular, if the tube component is heated by heat of the heating coils that are disposed within the upper and lower molds, the heating efficiency is not good. That is, only a portion of heat of the heating coil is transmitted to the tube component, and a majority portion of the heat is dissipated through the molds. In addition, because the heating coils are disposed within the upper and lower molds, it becomes difficult to manufacture such molds.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known to a person skilled in the art.